In recent years, a wireless data transmitting technique that uses an antenna coil to wirelessly transmit a power in a non-contact manner has been used in many devices such as an IC card and a cell phone. In a receiver including an antenna coil, a reception null point occurs due to a change in propagation environment, which deteriorates a reception property. In order to prevent the null point from occurring, there is proposed a method for improving the reception property by changing a device value of a device connected to the antenna coil.
However, when the method is applied to a radio device in which an antenna is shared between a transmitter and a receiver, there is a problem that a signal is leaked in transmission and reception, which deteriorates transmission/reception properties.